Weedwhacker motor, runs for a while then quits

I am trying to get an old weedwhacker motor running for conversion to a motored bike. It is still in the old weedwhacker frame. I can get it to run after it sits for a while and it will run well for less than a minute, then it just quits. I thought it was the carb so I bought a new one. After replacing the carb, it still does the same thing.

What would you do next to try to fix it? Maybe a new fuel line and filter? I have seen fuel running out of the fuel line, there does not seem to be an obstruction.

The motor is running rich right now. I will adjust the idle once I can keep it going for a couple of minutes. Could that be the problem?

Also, the carb has two gas line connections. I am thinking one is the return line, which I do not need for the weedwhacker set up. I am just plugging the return line.

I was going to say - fuel carb problem - same problem with new carb - like you say - return line ? Sure sounds like a fuel problem - although maybe condenser or coil - when slightly heated - shorting out ?? Let us know ok ? Happy Riding from - Mountainman